A UTH is an under tank heater. This can be in the form of a human heating pad or flexwatt heat tape. The reason for a dimmer is to cut the amount of power to the heat source which keeps the temps from getting out of control. UTHs can routinely reach upwards of 110 degrees. Enough for major thermal burns to your snakes. You can either get a lamp dimmer at the hardware store or a commercially made rheostat (sold at pet stores). Even better, go out and grab a thermostat and keep that temperature stable. Good luck!

Jamie